1. Field of the Invention
The invention relates to compositions for thermoplastic aliphatic polyesters, a process for their preparation, their use for the manufacture of films, foams, bottles or thermally molded products, the films, foams, bottles and thermally molded products obtained and the use of the films obtained.
2. Description of the Background
The thermoplastic aliphatic polyesters, and in particular the xcex5-caprolactone polymers, have a great many desirable properties, including a good biodegradability and good tensile strength. These properties make the thermoplastic aliphatic polyesters, and in particular the xcex5-caprolactone polymers, especially attractive in the polymer industry.
For many potential applications of the thermoplastic aliphatic polyesters, and in particular the xcex5-caprolactone polymers, it nonetheless is necessary that these polymers be characterized by a behavior of hardening under elongation in the molten state. There may be cited among these applications the films used, for example, for the making of trash bags, films for agriculture, films for packaging, shrouds, disposable diapers or adhesive films; foams, bottles and thermally molded products including, for example, pots for young plants.
Unfortunately, the thermoplastic polyesters and in particular the xcex5-caprolactone polymers, do not naturally display this behavior of hardening under elongation in the molten state.
It is known to increase the thermoresistance of xcex5-caprolactone polymers by bringing about their cross-linking through reaction with organic peroxides or through radiation with gamma rays. In these cases, however, the polymers obtained are characterized by a very high gel level (level of insoluble polymers) resulting in the occurrence of heterogeneous zones in the films which they form and consequently a poor surface quality of these films. In addition, very often there is noted a puncturing of the bubble which is obtained at the time of blowing, making the obtaining of a film impossible.
In addition, it also is known to add starch to the xcex5-caprolactone polymers so that the compositions obtained display the properties required to give rise to the manufacture of films (C. Bastioli, Macromol. Symp., 135, 193-204 (1998)). Unfortunately, the xcex5-caprolactone polymers present in these compositions are characterized disadvantageously by an excessively low crystallization speed, when the external temperature is too high, to ensure a sufficient output of the films formed.
This invention has the purpose of compositions for thermoplastic aliphatic polyesters, in particular for xcex5-caprolactone polymers, which do not display the aforesaid drawbacks.
This invention also has the purpose of a process for preparation of these compositions.
The invention further has the purpose of the use of these compositions for the manufacture of films, foams, bottles or thermally molded products as well as the films, foams, bottles and thermally molded products obtained and the use of the films obtained for manufacturing trash bags, films for agriculture, films for packaging, shrouds, disposable diapers and adhesive films.
To this end, the invention relates first of all to compositions for thermoplastic aliphatic polyesters characterized by an RMFI value ranging between 1.1 and 2.5.